The Search Engine List is a good list of available web search engines.
The all-in-one search page groups together several hundred different search engines, from Altavista down to browsing email addresses.
INSPEC is a catalogue of engineering, electronics and physics journal abstracts provided on CD-ROM.
MEDLINE is a similar catalogue for the biomedical sciences from the US national library of Medicine. The Hong Kong University Library provides a list of many such CD-ROM-based catalogues in varied domains.